Extrusion press machine and platen for extrusion press machine

ABSTRACT

An extrusion press machine includes: a die configured to extrusion-mold a workpiece; a cylinder configured to apply pressing force to press the workpiece against the die; and a platen configured to receive the pressing force from the die. The platen includes an outside element and an inside element that is disposed coaxially with the outside element, inside the outside element. The inside element includes one or more fluid supply structures each supplying a cooling medium toward an extruded product extruded from the die.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation of PCT Patent Application No. PCT/JP2019/038082filed Sep. 27, 2019. The content of this application is incorporated byreference herein in its entirety.

TECHNICAL FIELD

The present invention relates to an extrusion press machine used forextrusion molding of a metal such as an aluminum alloy, and inparticular, to a platen.

BACKGROUND ART

To extrusion-mold a metal material by an extrusion press machine, abillet is pressed with extruding force against a die disposed on aplaten through a pressure ring. The extruding force is applied by a maincylinder included in the extrusion press machine. When reaction force ofthe extruding force acts on the platen and a main cylinder housingduring an extrusion process, deflection occurs on the platen. With thedeflection of the platen, deflection occurs on the pressure ring and thedie. The platen may also be referred to as an end platen.

FIG. 9 illustrates deflection occurring on a platen 220.

As illustrated in an upper diagram of FIG. 9, reaction force f ofextruding force F acts on a substantially center part of the platen 220in an extrusion direction through a die 260 and a pressure ring 250. Theextrusion direction is the direction same as a direction of a void arrowindicating the extruding force F. In contrast, against the reactionforce f, drag f′ in a direction opposite to the direction of thereaction force f is generated in tie rods 287. The tie rods 287 resistthe reaction force f by deforming (extending) in a direction parallel tothe extrusion direction within an elastic range. As a result, a bendingmoment M bending the platen 220 to protrude the substantially centerpart of the platen 220 in the extrusion direction is generated in theplaten 220. However, in the platen 220 including a discharge path 242that penetrates through the platen 220 in a thickness direction tocontinuously extrusion-mold (discharge) a product rearward, it isphysically difficult to secure sufficient rigidity against the bendingmoment M near the discharge path 242. Therefore, during the extrusionprocess, deflection and bending deformation occur as illustrated in alower diagram of FIG. 9.

Although FIG. 9 is a schematic plan view, deflection of the platen 220occurs in a view from a side surface as in the plan view because the tierods 287 are disposed at four corners of the platen 220. In other words,in a three-dimensional view, deflection occurs such that thesubstantially center part of the platen 220 protrudes in the extrusiondirection.

Further, when the platen 220 is deflected by the extruding force Fduring the extrusion process, the pressure ring 250 and the die 260fixed to the platen 220 also deform with the deflection of the platen220.

The extruding force acting on the platen during the extrusion process isvaried, more specifically, is reduced as illustrated in FIG. 10 during aperiod from start to completion of the extrusion. Therefore, thedeflection of the platen 220 is reduced during the extrusion process.With reduction of the deflection, the deformation of the pressure ringand the die may be also reduced. Therefore, a dimension of a productextrusion-molded by the die is varied during the period from start tocompletion of the extrusion process, and it is difficult to obtaindesired dimensional accuracy of the product depending on a degree ofdeformation variation of the die. A lateral axis of a graph in FIG. 10indicates a length L of the billet during the extrusion process, and avertical axis indicates the extruding force F necessary for extrusionmolding of the billet. The extruding force F is expressed by a sum ofnecessary extruding force Fa acting on the die through the billet andfrictional force fb between an outer peripheral surface of the billetand an inner peripheral surface of a container housing the billet,namely, F=Fa+fb. The above-described reduction of the extruding forceduring the extrusion process is caused by reduction of the frictionalforce fb. Further, the necessary extruding force Fa is constant and isnot varied during the extrusion process by ignoring thermal influence.

Patent Literature 1 discloses a pressure ring with which deflectionduring an extrusion process can be suppressed, and an extrusion pressmachine using the pressure ring. The pressure ring disclosed in PatentLiterature 1 has a double structure including an outside member and aninside member, and the outside member is shrink-fitted to the insidemember. According to the pressure ring disclosed in Patent Literature 1,since the outside member is shrink-fitted to the inside member, stressfrom outside to inside in a radial direction is applied to the insidemember. Therefore, even when a load is applied in an axial direction ofthe pressure ring, the stress from outside to inside resists the load,which suppresses deflection.

CITATION LIST Patent Literature

Patent Literature 1: JP H10-258309 A

SUMMARY OF INVENTION Technical Problem

According to Patent Literature 1, it is possible to suppress deflectionof the pressure ring. However, the deflection of the pressure ring isbased on the deflection of the platen. Even when the stress from outsideto inside is generated in the pressure ring having the double structure,the deflection of the platen cannot be eliminated. Therefore, it isdifficult to suppress deformation variation of the pressure ring and thedie during the extrusion process, to a degree sufficient to obtain highdimensional accuracy of the product.

Therefore, an object of the present invention is to provide an extrusionpress machine including a platen in which occurrence of deflection canbe suppressed.

Solution to Problem

An extrusion press machine according to the present invention includes:a die configured to extrusion-mold a workpiece; a cylinder configured toapply pressing force to press the workpiece against the die; and aplaten configured to receive the pressing force from the die.

The platen according to the present invention includes an outsideelement and an inside element that is disposed coaxially with theoutside element, inside the outside element.

The inside element according to the present invention includes one ormore fluid supply structures each supplying a cooling medium toward anextruded product extruded from the die.

The inside element according to the present invention is preferablyprovided to sandwich the outside element from front and rear surfaces ofthe outside element.

In the platen according to the present invention, the outside elementand the inside element are preferably fitted, tensile stress ispreferably generated in an axial direction (C) in the inside element,and compression stress corresponding to the tensile stress is preferablygenerated in the outside element.

The inside element according to the present invention is preferablyprovided to sandwich the outside element by fastening.

In the platen according to the present invention, the outside elementand the inside element fitted to each other preferably have a gap in aportion not concerning fitting.

The inside element according to the present invention preferablyincludes a large-diameter portion provided on a front side, asmall-diameter portion continuous with the large-diameter portion, and afastening member fastened with the small-diameter portion.

The fastening member is fastened in advance with the small-diameterportion to press the outside element, and a preliminary load greaterthan or equal to a load acting during the extrusion process isaccordingly applied. As a result, tensile stress is generated in theinside element.

In the outside element according to the present invention, compressionstress is preferably generated in an area sandwiched by the insideelement.

The outside element according to the present invention preferablyincludes a first outside element adjacently fitted to outside of theinside element, and a second outside element adjacently fitted tooutside of the first outside element. The inside element is provided tosandwich the first outside element from front and rear surfaces of thefirst outside element.

Tensile stress is preferably generated in an axial direction (C) in theinside element, and compression stress corresponding to the tensilestress is preferably generated in the first outside element.

In the outside element according to the present invention, the firstoutside element and the second outside element are preferably fitted byshrinkage fit.

The inside element according to the present invention preferablyincludes a plurality of the aforementioned fluid supply structures (160)

The inside element according to the present invention is preferably madeof a metal material that has a longitudinal elastic modulussubstantially same as or greater than a longitudinal elastic modulus ofthe outside element.

Advantageous Effects of Invention

According to the present invention, the inside element sandwiches theoutside element from the front and rear surfaces of the outside element.The sandwiching generates the tensile stress in the inside element andgenerates the compression stress in the outside element. Therefore, evenwhen a load acts in the extrusion direction during the extrusionprocess, the tensile stress generated in the inside element and thecompression stress generated in the outside element are maintained whilebeing reduced. Thus, even if deflection occurs on the outside element, aportion where the tensile stress or the compression stress is generatedis hardly deflected.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a partial cross-sectional plan view illustrating a schematicconfiguration of an extrusion press machine including a platen accordingto a first embodiment.

FIG. 2 is a partial cross-sectional plan view illustrating aconfiguration of the platen in FIG. 1 and an enlarged view of a partthereof.

FIG. 3 is an axially-exploded view illustrating the platen in FIG. 2.

FIG. 4 is a diagram illustrating another form of the platen in FIG. 2.

FIG. 5 is a front view illustrating a platen according to a secondembodiment.

FIG. 6 is a partial cross-sectional plan view illustrating aconfiguration of the platen in FIG. 5.

FIG. 7 is an axially-exploded view illustrating the platen in FIG. 6.

FIG. 8 is a cross-sectional view illustrating a configuration of a fluidsupply structure 160 provided in the platen in FIG. 6.

FIG. 9 is a diagram to explain deflection occurring in a platen.

FIG. 10 is a graph illustrating variation of extruding force F during anextrusion process.

DESCRIPTION OF EMBODIMENTS

An extrusion press machine according to the present invention isdescribed below based on embodiments. The extrusion press machineaccording to the embodiments includes a platen including a plurality ofelements divided in a radial direction. Among the plurality of dividedelements, an element disposed on an inside (i.e., inside element) isfixed with a pressure ring. The inside element penetrates an element(s)disposed outside the inside element and sandwich the element(s) disposedon the outside from front and rear surfaces. Since the platen accordingto the embodiments has such a structure, deflection during the extrusionprocess can be suppressed.

The embodiments include a first embodiment in which the platen has astructure divided into two elements in the radial direction, and asecond embodiment in which the platen has a structure divided into threeelements in the radial direction. The first embodiment and the secondembodiment are described below in order.

First Embodiment

Based on an extrusion press machine 1 according to the first embodiment,a platen 20 according to the present embodiment is described.

As illustrated in FIG. 1, the extrusion press machine 1 includes anextrusion unit 10 from which a billet B as a workpiece is extruded, aholding unit 70 housing and holding the billet B, and a pressuregeneration unit 80 generating a load to press the billet B housed in theholding unit 70, toward the extrusion unit 10. The platen 20 is a mainelement configuring the extrusion unit 10.

Extrusion Unit 10

As illustrated in FIG. 1, FIG. 2, and FIG. 3, the extrusion unit 10includes the platen 20, a pressure ring 50 supported by the platen 20,and a die 60 supported by the pressure ring 50.

The platen 20 includes an outside element 30 and an inside element 40that is coaxially supported inside the outside element 30 by fitting,and has a two-layer structure divided in the radial direction.

Outside Element 30

As illustrated in FIG. 2 and FIG. 3, the outside element 30 is arectangular parallelepiped member including a thick portion 31 providedon a rear side and a thin portion 33 continuous with the thick portion31 and is provided on a front side. A “thickness” of each of the thickportion 31 and the thin portion 33 indicates a distance from an innerperipheral surface of a holding hole 35 described below to an outerperipheral surface of the outside element 30. The outside element 30includes the holding hole 35 that is provided inside the thick portion31 and the thin portion 33 and penetrates through the outside element 30in a front-rear direction. The inside element 40 is fitted to theholding hole 35. The holding hole 35 includes a small-inner-diameterportion 36 corresponding to the thick portion 31, and alarge-inner-diameter portion 37 corresponding to the thin portion 33,and is formed in a step shape in the front-rear direction. The outsideelement 30 is normally made of cast iron. The inside element 40 issimilarly fabricated.

In the extrusion press machine 1, a side (F) illustrated in FIG. 1 isdefined as a front side, and a side (B) is defined as a rear side.Further, a dimension in the radial direction is determined based on acenter axis C illustrated in FIG. 1 and FIG. 2.

Inside Element 40

As illustrated in FIG. 2 and FIG. 3, the inside element 40 is acylindrical member including a large- diameter portion 41 provided withan attachment surface 48 for the pressure ring 50, and a small-diameterportion 43 continuous with the large-diameter portion 41 and is providedso as to penetrate through the thick portion 31 in the front-reardirection. The inside element 40 has an appearance similar to a bolt.The large-diameter portion 41 corresponds to a head portion, and thesmall-diameter portion 43 corresponds to a shank portion.

An outer diameter of the inside element 40 is smaller than a length ofeach of outer surfaces (top and bottom surfaces and both side surfaces)of the outside element 30, and is considered to substitute a part on theinner diameter side of the outside element 30. When a preliminary loadis acted, surface pressure ΔP described below corresponding to thepreliminary load is generated on a pressure receiving surface 32 of theoutside element 30 (thick portion 31) in FIG. 2. The diameter of each ofthe large-diameter portion 41 and the small-diameter portion 43 of theinside element 40 determining an area of the ring-shaped pressurereceiving surface 32 is determined in consideration of a diameter of theused die 60 and a diameter of the pressure ring 50, such that thesurface pressure ΔP becomes lower than a yield point of the materialstrength of the outside element 30 in anticipation of safety factor.

ΔP=A/F

A=π·(D ² −d ²)/4

ΔP: surface pressure of pressure receiving surface 32

F: extruding force (preliminary load MF)

A: area of pressure receiving surface 32

φD: outer diameter of large-diameter portion 41

φd: outer diameter of small-diameter portion 43

The inside element 40 includes a discharge path 42 that penetratesthrough the inside element 40 from the large-diameter portion 41 to thesmall-diameter portion 43 in the front-rear direction. An extrudedproduct extruded through the die 60 passes through the discharge path 42and is discharged rearward from the extrusion press machine 1. Theinside element 40 further includes a male thread 44 on an outerperipheral end on the rear side of the small-diameter portion 43. Themale thread 44 of the small-diameter portion 43 is fastened with afemale thread 47 of a fastening member 46 described below. The insideelement 40 further includes a pressure receiving surface 45 connectingthe large-diameter portion 41 and the small-diameter portion 43. Thepressure receiving surface 45 is a surface receiving pressure from theoutside element 30 in a direction parallel to the center axis C, namely,in an axial direction. As the pressure receiving surface 45 and thepressure receiving surface 32 of the outside element 30, planesorthogonal to the center axis C are illustrated; however, the pressurereceiving surface 45 and the pressure receiving surface 32 may have theother shapes as long as the pressure receiving surface 45 and thepressure receiving surface 32 can receive pressure from each other. Forexample, tapered surfaces inclined in an extrusion direction Ed (FIG. 1)or step-shaped surfaces can be adopted.

The inside element 40 includes the fastening member 46 to fix thelarge-diameter portion 41 and the small-diameter portion 43 to theoutside element 30. The fastening member 46 has a form similar to a nut,and includes, on the inner peripheral surface, the female thread 47 tobe fastened with the male thread 44 provided in the small-diameterportion 43. The first embodiment is characterized in that, in a statewhere the preliminary load MF is generated during assembly of theextrusion press machine 1, tensile stress PF in the direction parallelto the center axis C is constantly generated in the inside element 40 byfastening the fastening member 46 in advance with the small-diameterportion 43 from the rear side of the platen 20.

The preliminary load MF is set to a value greater than or equal to arated load acting on the inside element 40 through the pressure ring 50and the die 60 during the extrusion process. An example of a procedureto generate the preliminary load MF is described below.

In the first embodiment, at least the male thread 44 of thesmall-diameter portion 43 protrudes rearward from the outside element30, and the female thread 47 of the fastening member 46 is fastened withthe male thread 44. As a result, the thick portion 31 of the outsideelement 30 is sandwiched by the inside element 40 and the fasteningmember 46 that are fastened with each other.

The fastening member 46 is required to be screwable to the male thread44 of the inside element 40 from the rear side of the platen 20 and toinclude the discharge path 42 to discharge the product extruded from thedie 60, from the platen 20. As long as the fastening member 46 satisfiesthe requirements, a female thread 44′ processed on the inner peripheralsurface of the small-diameter portion 43 of the inside element 40 and amale thread 47′ processed on the outer peripheral surface of a portionprotruding from a fastening member 46′ to the inner peripheral surfaceof the small-diameter portion 43 may be fastened as illustrated in FIG.4.

Pressure Ring 50

As illustrated in FIG. 1 to FIG. 3, the pressure ring 50 is attached tothe attachment surface 48 of the inside element 40 with unillustratedbolts or the like, and receives pressing force from the die 60 andtransmits the pressing force to the inside element 40. The pressure ring50 includes a passage 51 communicating with the discharge path 42 of theinside element 40. The pressure ring 50 is made of a material higher instrength than the outside element 30 and the inside element 40, forexample, tool steal.

Holding Unit 70

As illustrated in FIG. 1, the holding unit 70 includes a container 71holding the billet B, a container holder 73 holding the container 71,and a container cylinder 75 pressing the container 71 against the die 60through the container holder 73.

The container 71 includes a holding chamber 72 penetrating through thecontainer 71 in the front-rear direction while being supported by thecontainer holder 73. The billet B is held by the container 71 whilebeing housed in the holding chamber 72.

The container holder 73 holds the container 71. The container 71 held bythe container holder 73 can reciprocate in the front-rear direction,integrally with the container holder 73.

The container cylinder 75 includes a cylinder 76 fixed to the platen 20,and a piston rod 77 provided so as to advance and retreat to/from thecylinder 76. The piston rod 77 has a front end portion fixed to thecontainer holder 73. When the container cylinder 75 is operated, thecontainer 71 can be pressed against the die 60 through the containerholder 73.

Pressure Generation Unit 80

As illustrated in FIG. 1, the pressure generation unit 80 includes amain cylinder housing 81 disposed to face the platen 20, and a maincylinder 83 supported at substantially center of the main cylinderhousing 81. The pressure generation unit 80 further includes a sidecylinder 85 supported by the main cylinder housing 81 on a periphery ofthe main cylinder 83, and tie rods 87 supported by the main cylinderhousing 81 on a periphery of the main cylinder 83.

The main cylinder 83 includes a main ram 84, a main crosshead 86 fixedto a front end of the main ram 84, and an extrusion stem 88 attached tothe main crosshead 86. When the main cylinder 83 operates the main ram84 toward the platen 20, the extrusion stem 88 presses the billet Bagainst the die 60.

The tie rods 87 and tie rod nuts 89 couple the main cylinder housing 81and the platen 20. The tie rods 87 and the tie rod nuts 89 couple fourcorners of the platen 20 and corresponding four corners of the maincylinder housing 81. During the extrusion process, reaction force of theextruding force acts on the platen 20 through the die 60 and thepressure ring 50 and acts on the main cylinder housing 81 through themain cylinder 83 in a direction in which the platen 20 and the maincylinder housing 81 are separated from each other. The tie rod nuts 89configuring large-diameter portions of the respective tie rods 87restrain movement of the platen 20 and the main cylinder housing 81against the reaction force. Each of the tie rods 87 is configured tohave strength resisting against the reaction force of the extrudingforce while allowing extension of the tie rod 87 in the elastic region.

Operation of Extrusion Press Machine 1

Operation of the extrusion press machine 1 including the above-describedconfiguration is described.

To extrusion-mold the billet B as the workpiece by the extrusion pressmachine 1, the container cylinder 75 presses the container 71 againstthe die 60 disposed on the platen 20 through the pressure ring 50 byunillustrated holding means. Further, the extrusion stem 88 is movedtoward the platen 20 to press the billet B housed in the container 71,against the die 60. This process is called an upset process. The mainram 84 is further moved toward the platen 20 to cause the extrusion stem88 to press the billet B against the die 60, thereby continuouslyextrusion-molding a predetermined product rearward from a die hole 61 ofthe die 60. The process is called the extrusion process. Note that acylinder rod of the side cylinder 85 is also fixed to the main crosshead86, and the side cylinder 85 is driven during the extrusion process,namely, when the main crosshead 86 is advanced and retreated.

Procedure to Generate Tensile Stress PF

Next, an example of a procedure to generate the tensile stress PF inadvance in a direction parallel to the center axis C in the insideelement 40 by the preliminary load MF is briefly described withreference to FIG. 1 to FIG. 3.

Temporary Fixing of Outside Element 30 and Inside Element 40

First, the pressure ring 50 is fixed to the attachment surface 48 of theinside element 40 of the platen 20 with unillustrated bolts or the like.At this point, the fastening member 46 is detached.

Subsequently, the inside element 40 to which the pressure ring 50 hasbeen fixed is inserted into the holding hole 35 of the outside element30 of the platen 20 by a crane, a dedicated insertion tool, or the like.The outer diameter of the small-diameter portion 43 of the insideelement 40 and the inner diameter of the small-inner-diameter portion 36of the holding hole 35 have a clearance satisfying positioning criteriaof the inside element 40 to the outside element 30. Therefore, it is notparticularly necessary to position the inside element 40 to the outsideelement 30. On the other hand, an opening diameter of a housing chamber39 in which the large-diameter portion 41 is to be housed is greaterthan the outer diameter of the large-diameter portion 41 of the insideelement 40 (FIG. 2), and a predetermined clearance S is secured. Theopening diameter of the housing chamber 39 indicates the inner diameterof the large-inner-diameter portion 37 of the holding hole 35. Theclearance S is described below. In this state, a part of the male thread44 of the small-diameter portion 43 of the inside element 40 is exposedrearward from the outside element 30. The female thread 47 of thefastening member 46 is screwed to the male thread 44 by using a crane, adedicated insertion tool, or the like, thereby temporarily fastening thefastening member 46 with the small-diameter portion 43.

Action of Preliminary Load MF

Next, the preliminary load MF greater than or equal to a load (ratedload) acting in the extrusion direction Ed during the extrusion process,is applied between the platen 20 and the main cylinder housing 81. Morespecifically, in place of the die 60, for example, a dummy die that hasa product shape but has no opening is disposed on the pressure ring 50by unillustrated holding means, and the container cylinder 75 pressesthe container 71 in which no billet B is housed, against the dummy die.

Thereafter, the main cylinder 83 and the side cylinder 85 are driven,the extrusion stem 88 including an unillustrated extrusion tool or thelike attached to the front end thereof is moved toward the platen 20inside the holding chamber 72 of the container 71, thereby directlyapplying the extruding force to the dummy die by the extrusion tool. Atthis time, hydraulic oil pressure supplied to the main cylinder 83 andthe side cylinder 85 is controlled such that the extruding force(preliminary load MF) applied between the platen 20 and the maincylinder housing 81 through the dummy die is greater than or equal tothe load (rated load) acting in the extrusion direction Ed during theextrusion process. The preliminary load MF is preferably set to 105% to110% of the rated load.

When the preliminary load MF greater than the rated load is applied, theplaten 20 is largely compressed through the pressure receiving surface45 of the inside element 40, as compared with during the extrusionprocess with the rated load.

Retightening of Fastening Member 46

Further, in this state, the fastening member 46 temporarily fastened isscrewed to the male thread 44 of the small-diameter portion 43 of theinside element 40 from the rear side of the platen 20 by a dedicatedscrewing tool or the like, so as to be retightened. Since thepreliminary load MF is applied to the inside element 40 in the extrusiondirection Ed, rotation stopper means to restrain relative rotary motionof the inside element 40 to the outside element 30 is unnecessary.Further, the outside element 30 included in a projection area of thepressure receiving surface 45 in the extrusion direction Ed is furthercompressed as compared with during the extrusion process with the ratedload. Therefore, the tensile stress PF corresponding to the preliminaryload MF can be constantly generated in the direction parallel to thecenter axis C of the inside element 40 without applying large screwingforce, when the preliminary load MF is released after the fasteningmember 46 is screwed to the small-diameter portion 43 of the insideelement 40.

Effects by First Embodiment

Next, effects by the platen 20 according to the first embodiment aredescribed. The effects include a first effect by generation of theabove-described stress state between the outside element 30 and theinside element 40, and a second effect by provision of the clearance S.The effects are described in order below.

First Effect by Stress State between Outside Element 30 and InsideElement 40

In the first embodiment, the inside element 40 sandwiches the outsideelement 30 from the front and rear surfaces of the outside element 30.As a result, the tensile stress PF is generated in the inside element 40in the direction parallel to the center axis C, and compression stressCF is generated on a portion of the outside element 30 sandwichedbetween the pressure receiving surface 45 of the inside element 40 andthe fastening member 46. The tensile stress PF and the compressionstress CF are each corresponding to the preliminary load MF greater thanthe rated load. Therefore, even when the load acting in the extrusiondirection Ed during the extrusion process is the maximum, namely, issubstantially equal to the rated load, the tensile stress PF generatedin the inside element 40 and the compression stress CF generated in theoutside element 30 are maintained while being reduced. Therefore, evenwhen the tie rods 87 are extended and deflection occurs on the outsideelement 30 of the platen 20, the fastening state of the inside element40 and the fastening member 46 at the substantially center part of theplaten 20 is maintained, and deflection hardly occurs.

As described above, according to the present embodiment, the fasteningstate of the inside element 40 and the fastening member 46 at thesubstantially center part of the platen 20 and the compression stress CFin the fastening state are maintained during the extrusion process.Therefore, even when the discharge path 42 through which the product isextruded and discharged to the rear side of the platen 20 is provided inthe inside element 40, rigidity sufficient to resist a bending moment M(FIG. 9) that causes deflection on the platen 20, in particular, on theoutside element 30, can be secured at the portion of the thick portion31 of the outside element 30 held by the inside element 40(large-diameter portion 41) and the fastening member 46, near thedischarge path 42. Thus, according to the first embodiment, it ispossible to exert the first effect to suppress deflection of the platen20.

Second Effect by Provision of Clearance S

In the first embodiment, providing the clearance S makes it possible tosuppress, even when deflection occurs on the platen 20, influence of thedeflection on the pressure ring 50. The effect is described below withreference to a partial enlarged view of FIG. 2.

In the partial enlarged view, a state before deflection occurs on theoutside element 30 is illustrated by a two-dot chain line, and a stateafter deflection occurs is illustrated by a solid line. The clearance Sis provided between the outside element 30 and the inside element 40.The clearance S is a gap provided in a portion not concerning fitting ofthe outside element 30 and the inside element 40. The clearance S is setsuch that, even when deflection as illustrated occurs on the platen 20,in particular, on the outside element 30, an inner peripheral surface 38defining the housing chamber 39 does not come into contact with thelarge-diameter portion 41 of the inside element 40.

With this configuration, deflection of the outside element 30 does notdirectly influence on deformation of the pressure ring 50. Therefore,even in the case where deflection occurs on the outside element 30 andthe deflection (deflection amount) is varied due to variation(reduction) of the extruding force F, the die 60 disposed on thepressure ring 50 by the unillustrated holding means is not deformed asthe second effect. Further, as described above, only the clearancesatisfying the positioning criteria of the inside element 40 to theoutside element 30 is provided between the outer diameter of thesmall-diameter portion 43 of the inside element 40 and the openingdiameter of the holding hole 35 into which the small-diameter portion 43is inserted. However, in the state where deflection occurs on theoutside element 30, most part of an inner peripheral surface (innerperipheral surface of small-inner-diameter portion 36) of the opening ofthe outside element 30 into which the small-diameter portion 43 isinserted deforms in the direction separating from the outer peripheralsurface of the small-diameter portion 43 of the inside element 40.Therefore, when deflection occurs on the outside element 30, smallnessof the clearance does not influence on deformation of the pressure ring50. Note that the predetermined clearance S and the deflection of theoutside element 30 in FIG. 2 are exaggerated to facilitate understandingof the description.

On the other hand, during the extrusion process, rigidity to resist thebending moment M that causes deflection on the outside element 30,secured by maintaining the fastening state of the inside element 40 andthe fastening member 46 at the substantially center part of the outsideelement 30 and maintaining the compression stress CF in the fasteningstate, can be structurally secured even when the inside element 40 ismade of a metal material having a longitudinal elastic modulussubstantially same as a longitudinal elastic modulus of the platen 20.Therefore, the inside element 40 is manufactured by a metal materialgreater in longitudinal elastic modulus than the platen 20, to improvethe strength itself of the substantially center part of the platen 20 inaddition to the compression stress CF generated at that center part.This makes it possible to further enhance the rigidity.

As described above, the tensile stress PF is generated in the insideelement 40 and the compression stress CF is generated in the outsideelement 30 by the inside element 40 and the fastening member 46. Thismakes it possible to improve rigidity at the substantially center partof the outside element 30 and to suppress deflection (deflection amount)of the outside element 30 during the extrusion process.

Further, even when deflection (deflection amount) occurs on the outsideelement 30 and the deflection is varied during the extrusion process byvariation (reduction) of the extruding force F, the predeterminedclearance S is secured while being reduced by the configuration in whichthe outer peripheral surface of the large-diameter portion 41 of theinside element 40 and the inner peripheral surface of the holding hole35 of the outside element 30 in which the large-diameter portion 41 isdisposed do not come into contact with each other. Therefore, thedeflection of the outside element 30 does not directly influence ondeformation of the pressure ring 50.

As a result, as compared with the extrusion press machine disclosed inPatent Literature 1, deformation (deformation amount) of the pressurering 50 and the die 60 and variation of the deformation can beconsiderably suppressed during the extrusion process, and it is possibleto obtain the product extrusion-molded by the die 60, with desireddimensional accuracy from start to completion of the extrusion process.

Second Embodiment

Next, a platen 120 according to a second embodiment of the presentinvention is described with reference to FIG. 5 to FIG. 8.

As illustrated in FIG. 5 and FIG. 6, the platen 120 according to thesecond embodiment has a three-layer structure including a second outsideelement 130, a first outside element 140, and an inside element 150. Thesecond outside element 130 is a rectangular parallelepiped member. Thefirst outside element 140 and the inside element 150 are cylindricalmembers and are coaxially disposed on the center axis C. The firstoutside element 140 is fitted to an inside of the second outside element130, and the inside element 150 is fitted to an inside of the firstoutside element 140. The inside element 150 is provided to sandwich thefirst outside element 140 from front and rear surfaces of the firstoutside element 140.

Second Outside Element 130

As illustrated in FIG. 5, FIG. 6, and FIG. 7, the second outside element130 includes a thick portion 131 provided on the rear side, and a thinportion 133 continuous with the thick portion 131 and is provided on thefront side. The second outside element 130 includes a holding hole 135that is provided inside the thick portion 131 and the thin portion 133and penetrates through the second outside element 130 in the front-reardirection. The first outside element 140 is fitted to the holding hole135. The holding hole 135 includes a small-inner-diameter portion 136corresponding to the thick portion 131, and a large-inner-diameterportion 137 corresponding to the thin portion 133, and is formed in astep shape in the front-rear direction.

First Outside Element 140

As illustrated in FIG. 5, FIG. 6, and FIG. 7, the first outside element140 includes a small-diameter portion 141 provided on the rear side, anda large-diameter portion 143 continuous with the small-diameter portion141 and is provided on the front side. The first outside element 140includes a holding hole 145 that penetrates through the small-diameterportion 141 and the large-diameter portion 143. The adjacent insideelement 150 is fitted to the holding hole 145. The holding hole 145includes a small-inner-diameter portion 146 and a large-inner-diameterportion 147, and is formed in a step shape in the front-rear direction.

The second outside element 130 and the first outside element 140 arepreferably fitted by shrinkage fit. When the second outside element 130and the first outside element 140 are fitted by the shrinkage fit,compression stress is generated between the second outside element 130and the first outside element 140 in a radial direction. Therefore, aportion including the second outside element 130 and the first outsideelement 140 is greater in rigidity than a case where the portion has anintegrated structure. Further, when a longitudinal elastic modulus of amaterial configuring the first outside element 140 is greater than alongitudinal elastic modulus of a material configuring the secondoutside element 130, rigidity of the second outside element 130 can befurther improved.

As described above, when the sufficient rigidity of the second outsideelement 130 is secured, the clearance S provided in the configuration ofthe first embodiment can be minimized or eliminated.

As the shrinkage fit, shrink fit and cooling fit are known. In a casewhere the shrink fit is adopted, the second outside element 130 and thefirst outside element 140 are fitted in a state where the second outsideelement 130 is heated to a predetermined temperature and is expanded inthe radial direction. In a case where the cool fit is adopted, thesecond outside element 130 and the first outside element 140 are fittedin a state where the first outside element 140 is cooled to apredetermined temperature and is shrunk in the radial direction.

Inside Element 150

As illustrated in FIG. 5, FIG. 6, and FIG. 7, the inside element 150includes a large-diameter portion 151 provided with an attachmentconcave portion for the pressure ring 50, and a small-diameter portion153 continuous with the large-diameter portion 151 and penetratesthrough the housing chamber 39 in the front-rear direction.

The inside element 150 includes a discharge path 152 that penetratesthrough the inside element 150 from the large-diameter portion 151 tothe small-diameter portion 153 in the front-rear direction. An extrudedproduct extruded through the die 60 passes through the discharge path152 and is discharged rearward from the extrusion press machine 1. Theinside element 150 further includes a male thread 154 on an outerperipheral end on the rear side of the small-diameter portion 153. Themale thread 154 of the small-diameter portion 153 is screwed with afemale thread 157 of a fastening member 156. The inside element 150further includes a pressure receiving surface 155 connecting thelarge-diameter portion 151 and the small-diameter portion 153. Thepressure receiving surface 155 is a surface receiving pressure from thesecond outside element 130 and the first outside element 140 in adirection parallel to the center axis C.

The inside element 150 includes the fastening member 156 to fix thelarge-diameter portion 151 and the small-diameter portion 153 to thefirst outside element 140. The fastening member 156 has a form similarto a nut, and includes, on the inner peripheral surface, the femalethread 157 to be fastened with the male thread 154 provided in thesmall-diameter portion 153. Also in the second embodiment, in a statewhere the preliminary load MF is generated during assembly of theextrusion press machine 1, the inside element 150 is disposed at thesubstantially center inner part of the platen 120 while tensile stressPF in the direction parallel to the center axis C is constantlygenerated in the inside element 150 by fastening the fastening member156 in advance with the small-diameter portion 153 from the rear side ofthe platen 120.

The inside element 150 is fixed to the first outside element 140 whilethe tensile stress PF is generated in advance in the extrusiondirection, by the preliminary load MF greater than or equal to the loadacting in the extrusion direction during the extrusion process. Therelationship is the same as the stress relationship between the outsideelement 30 and the inside element 40 in the first embodiment.

The inside element 150 includes fluid supply structures 160. Asillustrated in FIG. 5, for example, the fluid supply structures 160 areprovided at four positions with equal intervals in a circumferentialdirection.

As illustrated in FIG. 6 to FIG. 8, each of the fluid supply structures160 includes a first structure 161 that supplies liquid fluid or gasfluid cooling the extruded product, and a second structure 165 thatsupplies air to form an air curtain.

The first structure 161 includes a first flow path 162 through which acooling medium supplied from an unillustrated supply source flows, andfirst nozzles 163, 163 ejecting the cooling medium having flowed throughthe first flow path 162. The first flow path 162 extends inside thesmall-diameter portion 153 of the inside element 150 from the rear sidetoward the front side. The first nozzles 163, 163 are connected to frontends of the first flow path 162, and each have an ejection port directedto the inside in the radial direction of the small-diameter portion 153.

The second structure 165 includes a second flow path 166 through whichthe air supplied from an unillustrated supply source flows, and a secondnozzle 167 provided at a front end of the second flow path 166. Thesecond flow path 166 extends inside the small-diameter portion 153 ofthe inside element 150 from the rear side toward the front side. Thesecond nozzle 167 is connected to the front end of the second flow path166 and has an ejection port directed to the inside in the radialdirection of the small-diameter portion 153.

The first structure 161 supplies the cooling medium to the extrudedproduct having just passed through the discharge path 152, namely,immediately after being extruded, and cools the extruded product so asto follow a desired temperature history, which achieves effects ofstrength improvement and the like derived from hardening and otherthermal treatment of the extruded product. The supplied cooling mediumis selected from gas such as air and inert gas, and liquid such aswater. In terms of cooling capacity, liquid, in particular, water ispreferably sprayed.

When the liquid is used as the cooling medium, corrosion at a part wherethe sprayed liquid is adhered is concerned. For example, it is desirableto avoid occurrence of problem that the sprayed liquid adheres to thedie 60 through the discharge path 152 of the inside element 150 and thepassage 51 of the pressure ring 50, and the die 60 rusts or generatedrust is mixed into the extruded product. Therefore, in the presentembodiment, the second structure 165 is provided as a preferable form.In other words, the second structure 165 is provided on the front sideclose to the die 60 more than the first structure 161, and the air issupplied from the second structure 165 to form the air curtain thatprevents the liquid sprayed from the first structure 161 from reachingthe die 60.

In this example, the configuration in which the liquid is sprayed fromthe first structure 161 to the extruded product is described as thepreferable form; however, gas may be sprayed from the first structure161 to the extruded product. In this case, possibility of corrosion ofthe die 60 is eliminated. Therefore, the second structure 165 can beomitted.

Further, as illustrated in an upper diagram of FIG. 8, each of the fluidsupply structures 160 may be provided such that the first nozzles 163and the second nozzle 167 are exposed to the inside of the insideelement 150 through short pipes. Alternatively, as illustrated in alower diagram of FIG. 8, the first nozzles 163 and the second nozzle 167may be provided in concave portions processed on the inner peripheralsurface of the inside element 150. In a former case, a protector 164covering the first nozzles 163 and the second nozzle 167 is preferablyprovided.

Effects by Second Embodiment

Next, effects by the second embodiment are described.

The platen 120 according to the second embodiment has the three-layerstructure including the second outside element 130, the first outsideelement 140, and the inside element 150 in the radial direction, and thestress structure by sandwiching similar to that in the first embodimentis provided between the first outside element 140 and the inside element150. Therefore, as in the first embodiment, deformation of the platen120 during the extrusion process is suppressed.

Further, when the second outside element 130 and the first outsideelement 140 are fitted by shrinkage fit, compression stress in theradial direction is generated between the second outside element 130 andthe first outside element 140. Therefore, the portion including thesecond outside element 130 and the first outside element 140 is greaterin rigidity than the case where the portion has an integrated structure,and it is expected that deformation of the platen 120 during theextrusion process is further suppressed. As described above, whensufficient rigidity of the second outside element 130 is secured, theclearance S provided in the configuration of the first embodiment can beminimized or eliminated.

Further, in the second embodiment, since the fluid supply structures 160are provided in the inside element 150, it is possible to securerigidity of the second outside element 130 and the first outside element140 of the platen 120 as described below.

For example, it is assumed that drilling is performed in order to formthe first flow path 162 and the second flow path 166 of each of thefluid supply structures 160 around the discharge path 242 of the platen220 that is wholly integrally configured as illustrated in FIG. 9. Inthis case, if the platen 220 is deflected, stress concentrates ondrilled portions, which may cause breakage of the platen 220.

In place of the drilling, pipes configuring the first flow path 162 andthe second flow path 166 may be disposed on a peripheral edge of thedischarge path 242. To adopt the alternative, however, it is necessaryto increase the opening diameter of the discharge path 242 inconsideration of rising heights of cooling nozzles corresponding to thefirst nozzles 163 and the second nozzle 167. Therefore, when thealternative is adopted, rigidity of the platen 220 is deteriorated.

In contrast, in the second embodiment, the first flow path 162, thesecond flow path 166, the first nozzles 163, and the second nozzle 167are disposed inside the inside element 150. At this time, as describedabove in the first embodiment (paragraph 0048), in the state wheredeflection occurs on the outside element 30 in the first embodiment,most part of the inner peripheral surface (inner peripheral surface ofsmall-inner-diameter portion 36) of the opening of the outside element30 into which the small-diameter portion 43 is inserted deforms in thedirection separating from the outer peripheral surface of thesmall-diameter portion 43 of the inside element 40. Likewise, in a casewhere deflection occurs on the second outside element 130 in the secondembodiment, most part of the inner peripheral surface (inner peripheralsurface of small-inner-diameter portion 146) of the opening of thesecond outside element 130 into which the small-diameter portion 153 isinserted deforms in the direction separating from the outer peripheralsurface of the small-diameter portion 153 of the inside element 150.Accordingly, in the inside element 150, stress concentration caused bydeflection of the second outside element 130 does not occur, anddeterioration of rigidity does not occur because of the tensile stressPF corresponding to the preliminary load MF greater than the rated load,constantly generated in the direction parallel to the center axis C ofthe inside element 150.

Further, the stress structure by sandwiching in which the portionincluding the small-diameter portion 141 of the first outside element140 that is a part of the platen 120 is held by fastening of the insideelement 150 and the fastening member 156, and the compression stress CFat the portion is maintained is provided similar to that in the firstembodiment. The stress structure secures sufficient rigidity to resistthe bending moment M causing deflection of the platen 120, whichsuppresses deflection itself of the platen 120 during the extrusionprocess. As a result, it is possible to avoid stress concentration onthe first outside element 140 and the second outside element 130provided outside the inside element 150, and to avoid deterioration inrigidity.

Further, the inside element 150 that is smaller in dimension and weightthan the integrated platen 220 is easily drilled as compared withdrilling of the platen 220.

Although the preferred embodiments of the present invention have beendescribed above, the configurations described in the above-describedembodiments can be selected or replaced with other configurationswithout departing from the gist of the present invention. For example,the fluid supply structures 160 can be provided in the inside element 40in the first embodiment.

REFERENCE SIGNS LIST

-   1 Extrusion press machine-   10 Extrusion unit-   20 Platen-   30 Outside element-   31 Thick portion-   32 Pressure receiving surface-   33 Thin portion-   33A Surface-   33B Surface-   35 Holding hole-   36 Small-inner-diameter portion-   37 Large-inner-diameter portion-   38 Inner peripheral surface-   39 Housing chamber-   40 Inside element-   41 Large-diameter portion-   42 Discharge path-   43 Small-diameter portion-   45 Pressure receiving surface-   46 Fastening member-   46′ Fastening member-   48 Attachment surface-   50 Pressure ring-   60 Die-   70 Holding unit-   71 Container-   72 Holding chamber-   73 Container holder-   75 Container cylinder-   76 Cylinder-   77 Piston rod-   80 Pressure generation unit-   81 Main cylinder housing-   83 Main cylinder-   84 Main ram-   85 Side cylinder-   86 Main crosshead-   87 Tie rod-   88 Extrusion stem-   89 Tie rod nut-   120 Platen-   130 Second outside element-   131 Thick portion-   133 Thin portion-   135 Holding hole-   136 Small-inner-diameter portion-   137 Large-inner-diameter portion-   140 First outside element-   141 Small-diameter portion-   143 Large-diameter portion-   145 Holding hole-   146 Small-inner-diameter portion-   147 Large-inner-diameter portion-   150 Inside element-   151 Large-diameter portion-   152 Discharge path-   153 Small-diameter portion-   155 Pressure receiving surface-   156 Fastening member-   160 Fluid supply structure-   161 First structure-   162 First flow path-   163 First nozzle-   165 Second structure-   166 Second flow path-   167 Second nozzle-   220 Platen-   242 Discharge path-   250 Pressure ring-   260 Die-   287 Tie rod-   B Billet-   C Center axis-   S Clearance

1. An extrusion press machine, comprising: a die configured toextrusion-mold a workpiece; a cylinder configured to apply pressingforce to press the workpiece against the die; and a platen configured toreceive the pressing force from the die, wherein the platen includes: anoutside element; and an inside element that is disposed coaxially withthe outside element, inside the outside element, and the inside elementincludes one or more fluid supply structures each supplying a coolingmedium toward an extruded product extruded from the die.
 2. Theextrusion press machine according to claim 1, wherein each of the fluidsupply structures includes a first structure supplying the coolingmedium, and the first structure includes a first flow path through whichthe cooling medium flows, and a first nozzle ejecting the cooling mediumhaving flowed through the first flow path.
 3. The extrusion pressmachine according to claim 2, wherein each of the fluid supplystructures includes a second structure supplying air to form an aircurtain, the second structure includes a second flow path through whichthe air flows, and a second nozzle ejecting the air having flowedthrough the second flow path, and the second nozzle is provided on aside close to the die more than the first nozzle.
 4. The extrusion pressmachine according to claim 2, wherein the fluid supply structures areprovided with equal intervals in a circumferential direction.
 5. Theextrusion press machine according to claim 2, wherein the inside elementincludes a large-diameter portion provided on a front side, and asmall-diameter portion continuous with the large-diameter portion, andthe first flow path extends inside the small-diameter portion from arear side to the front side, and the first nozzle has an ejection portdirected to an inside in a radial direction of the small-diameterportion.
 6. The extrusion press machine according to claim 3, whereinthe inside element includes a large-diameter portion provided on a frontside, and a small-diameter portion continuous with the large-diameterportion, and the second flow path extends inside the small-diameterportion from a rear side to the front side, and the second nozzle has anejection port directed to an inside in a radial direction of thesmall-diameter portion.
 7. The extrusion press machine according toclaim 3, wherein the air curtain is formed to prevent liquid as thecooling medium ejected from the first nozzle, from reaching the die. 8.The extrusion press machine according to claim 3, wherein, in each ofthe fluid supply structures, the first nozzle and the second nozzle areprovided to be exposed to an inside of the inside element through shortpipes, or the first nozzle and the second nozzle are provided in concaveportions provided on an inner peripheral surface of the inside element.9. The extrusion press machine according to claim 1, wherein the insideelement is provided to sandwich the outside element from front and rearsurfaces of the outside element.
 10. The extrusion press machineaccording to claim 9, wherein the inside element is disposed inside theoutside element while tensile stress is generated in advance in an axialdirection by a preliminary load greater than or equal to a load actingduring an extrusion process.
 11. The extrusion press machine accordingto claim 1, wherein the inside element is made of a metal material thathas a longitudinal elastic modulus substantially same as or greater thana longitudinal elastic modulus of the outside element.
 12. A platen foran extrusion press machine, the platen being configured to receivepressing force in extrusion molding by a die, the platen comprising anoutside element and an inside element that is disposed coaxially withthe outside element, inside the outside element, wherein the insideelement includes one or more fluid supply structures each supplying acooling medium toward an extruded product extruded from the die.